rotation driver - skipping backwards after 90 degrees
Use a single property driver variable



Using the transform channel type of driver variable with Eulers makes it ripe for gimbal lock.

Could someone please explain gimbal lock?

If instead single property is used



The equivalent of 

driven_needle.rotation_euler.x = driving_needle.rotation_euler.x / 10


it will work as expected, so 90 degrees becomes 9, 180 -> `18'  and so on.